Not Applicable.
Not Applicable.
The present embodiments relate to integrated circuit formation, and are more particularly directed to an ion source architecture for providing ion implantation to form integrated circuits.
Integrated circuits are immensely prevalent in all aspects of contemporary electronic technology. Indeed, vast resources are expended in developing and implementing integrated circuit technology in order to supply demands imposed by the consuming marketplace. In this regard, the efficient production of integrated circuits is critical, and the present embodiments are directed at such efficiency. Particularly, the present embodiments improve the efficiency for building integrated circuits on a wafer or the like by improving the efficiency of the ion source architecture for providing ion implantation to the wafer. This as well as other benefits are explored later, but are first preceded by a discussion of the prior art.
By way of introduction, FIG. 1 illustrates a general view of various components of a prior art ion source architecture 10. Architecture 10 may include other components and could be illustrated and presented in still greater detail, but the illustration as shown and discussion below should be satisfactory to present one skilled in the art with a sufficient understanding of the prior art and for purposes of better appreciating the preferred embodiments discussed later. Turning to architecture 10, it includes an ion source 12 which includes various components described below, and as detailed below where during operation an ion beam 14 is extracted from source 12 so that ions are directed toward and implanted into an integrated circuit wafer 16. Looking in greater detail, ion source 12 includes an arc chamber 18 which has an interior area 18i for ion activity described below, and which includes an arc slit 18s which is an aperture through which ions may exit interior area 18i in the form of ion beam 14. Disposed through open ends of arc chamber 18 and through interior area 18i is a filament 20. Filament 20 at its ends 20p and 20n is connected to the positive and negative terminals, respectively, of a filament power supply 22. An arc power supply 24 has its negative terminal connected to the positive terminal of filament power supply 22 and its positive terminal connected to arc chamber 18. A positive terminal of an extraction power supply 26 is connected to the positive terminal of arc power supply 24, and the negative terminal of an extraction power supply 26 is connected to an extraction electrode 28 shown vertically in FIG. 1, and which includes an aperture 28a through which ion beam 14 may pass as further detailed below.
The operation of architecture 10 is now explored. Each of power supplies 22, 24, and 26 is energized, while wafer 16 is set at a potential which is low relative to that imposed on arc chamber 18 (e.g., wafer 16 may be set at ground or treated as a ground plane). The energizing of filament power supply 22 applies a potential across filament 20 which thereby causes filament 20 to heat; this heat is of a sufficient intensity so that electrons are emitted away from filament 20 into interior area 18i. In addition, the energizing of arc power supply 24 imposes a voltage on arc chamber 18 that is positive relative to that on filament 20 to thereby influence the direction of the electrons emitted by filament 20, primarily in an effort to maintain a heavy concentration of those electrons near the center of interior area 18i. Still further, one or more gases is typically provided into interior area 18i, although the apparatus for providing such gas is not shown in FIG. 1. In any event, the resultant electron and gas combination is often referred to in the art as a plasma, with its constituent parts also being referred to as ions. Magnets (not shown) are used to increase the electron mean free path further enhancing plasma generation. Lastly, the energizing of extraction power supply 26 imposes a voltage on extraction electrode 28 that is negative relative to that imposed on arc chamber 18, thereby attracting positive ions outward of slit 18s and producing a positive charged ion beam 14. Ion beam 14 passes through aperture 28a and impacts the surface of wafer 16, thereby implanting ions from beam 14 into wafer 16. Lastly, it is also known in the art to use one or more magnets (not shown) so as to divert some of the ion types away from wafer 16 so that only the remaining desired ions impact and thereby implant within wafer 16.
While architecture 10 has been successful for implanting ions in wafers, it also has various drawbacks. For example, recall that filament 20 passes through the center of interior area 18i, and also that it is desirable to maintain a heavy concentration of electrons near the center of interior area 18i. The resulting concentration of plasma at the center of interior area 18i tends to gradually wear filament 20 and, indeed, it is known that filament 20 will eventually fail (e.g., break), typically in response to this plasma exposure. This failure prohibits further use of architecture 10 until a satisfactory repair is made and, thus, there may be considerable down time in the operation of architecture 10. Such down time is considerably expensive when demand is to keep architecture 10 operating on a full-time basis, as is often the case in contemporary semiconductor fabrication facilities. As another disadvantage, the use of filament 20 as a single filament may have limitations on the amount of ion concentration it is capable of producing.
By way of further background, FIG. 2 illustrates an alternative prior art ion source architecture 30. To simplify this and the remaining prior art illustrations, some of the components in architecture 30 are the same as those shown with respect to architecture 10 of FIG. 1; as a result, these components and their reference numbers are carried forward from FIG. 1 and the reader is assumed familiar with the earlier discussion of such components. Looking then to the other components in architecture 30, it includes an ion source 32, which is sometimes referred to in the art as a Bernas source. Ion source 32 includes an arc chamber 34 which has an interior area 34i for ion activity and an arc slit 34s which through which ions may exit interior area 34i (as ion beam 14). Located proximate a first opening at a first end of arc chamber 34 is a filament 36, where filament 36 has a length 36ptl in the shape of a pigtail and which exists within interior area 34i, and where filament 36 further has ends 36p and 36n connected to the positive and negative terminals, respectively, of filament power supply 22. Located at a second end of arc chamber 34 is a reflector 38, where for reasons discussed below it should be noted that reflector 38 is therefore at an opposite end of arc chamber 34 relative to the location of filament 36. Reflector 38 includes a reflecting plate 38p which is typically a metal material, and plate 38p is supported by a support 38s which is an insulating material so as to electrically isolate plate 38p from arc chamber 34.
The operation of architecture 30 is similar in various respects to that of architecture 10, namely, in architecture 30 each of power supplies 22, 24, and 26 is energized and wafer 16 is set at a potential which is low relative to that imposed on arc chamber 34. In response, filament 36 heats and pigtail 36ptl emits electrons into interior area 34i, and these electrons are further directed toward the center of interior area 34i due to the electrical bias imposed on arc chamber 34 and additional source magnets (not shown). Once more, these electrons may be combined with one or more gases in interior area 34i to create a plasma from which ion beam 14 may be extracted. In addition, however, for architecture 30 reflector 38 also influences the directionality of the electrons in interior area 34. Particularly, when electrons are initially emitted by pigtail 36ptl and toward reflector plate 38p, plate 38p accumulates a negative charge. Thereafter, as additional electrons are emitted in the same manner, they are reflected away from plate 38p and again toward the center of interior area 34i. As a result, the concentration of electrons and, thus, the ion plasma density at the center of interior area 34i, is enhanced.
From the above, one skilled in the art will appreciate that architecture 30 also has been successful for implanting ions in wafers, but it too has various drawbacks. For example, filament 36, both in the portion forming pigtail 36ptl and a smaller portion that extends toward ends 36p and 36n, also is physically in contact with the plasma formed in interior area 34i and, once more, therefore this layout deteriorates the integrity of filament 36 such that it eventually fails in response to this contact. The deterioration may be improved as compared to architecture 10 since filament 36 does not extend to the absolute center of interior area 34i, but nonetheless the direct exposure of filament 36 to the plasma will cause an ultimate failure of filament 36. As with prior art architecture 10, such a break prohibits further use of architecture 30 until a satisfactory repair is achieved, thereby presenting the expense and other burdens associated with a considerable down time in the operation of architecture 30.
As still further background, FIG. 3 illustrates an alternative prior art ion source architecture 40. Architecture 40 includes an ion source 42 which is sometimes referred to in the art as an indirectly-heated cathode source for reasons more clear. With one exception, architecture 40 is the same as architecture 30 and, thus, for simplicity the common components and their reference numbers are carried forward from FIG. 2 to FIG. 3, with the reader being assumed familiar with the earlier discussion of such components. Looking to the one difference between architectures 40 and 30, filament 36 in ion source 42 is protected from interior area 34i by a cathode 44. Thus, filament 36 may extend into interior area 34i, but to the extent that it does so it is encased within the interior 44i defined by cathode 44. Typically, cathode 44 has a metallic end 44e, and its sides 44s are insulated from arc chamber 34 either by forming them from an insulating material or by separating cathode 44 from arc chamber 34 with air (i.e., by permitting a space between arc chamber 34 and cathode 44). The operational description below provides further insight as to the reasons for choosing such materials and the desirability of this insulating effect Lastly in connection with power to cathode 44, cathode 44 is biased by a positive terminal of a cathode power supply 45, where that positive terminal is also connected to the negative terminal of arc power supply 24. The negative terminal of cathode power supply 45 is connected to the positive terminal of filament power supply 22.
The operation of architecture 40 is similar in various respects to that of architecture 30 in that, once again, each of power supplies 22, 24, and 26 is energized, wafer 16 is set at a potential which is low relative to that imposed on arc chamber 34, filament 36 heats, and an ion beam 14 is extracted toward wafer 16. More particularly, however, for architecture 40 the heating of filament 36 transfers heat to cathode 44 and, thus, cathode 44 emits electrons. In this manner, therefore, the heat from filament 36 indirectly causes the emission of electrons into interior area 34i, thereby giving rise to the earlier-introduced xe2x80x9cindirectly-heatedxe2x80x9d identifier used in the art with respect to ion source 42. In any event, these indirectly generated electrons proceed in the same manner as described above and, thus, are directed toward the center of interior area 34i due to the operation of reflector 38 as well as the bias on arc chamber 34 and the source magnets (not shown).
Architecture 40 provides an improvement over architectures 10 and 30, but it also provides drawbacks. Turning first to the improvement, filament 36 is not exposed directly to the plasma within interior 34i because filament 36 is encased within cathode 44. Thus, the encasing effect of cathode 44 around filament 36 initially protects filament 36 from the plasma-created deterioration described above with respect to architectures 10 and 30. However, cathode 44 is itself exposed to the plasma; as a result, and as a drawback of architecture 40, at some point an aperture or other passage will form within cathode 44 and filament 36 is then exposed to the plasma. Accordingly, eventually filament 36 also will fail and, at that time, architecture 40 requires down time for repair.
As a final example, FIG. 4 illustrates an alternative prior art ion source architecture 50. Architecture 50 includes an ion source 52 which is sometimes referred to in the art as a double Bernas source since ion source 52 doubles the interior elements of the Bernas ion source 32 shown in FIG. 2. Thus, in addition to those elements shown in FIG. 2 (and carried forward into FIG. 4), an arc chamber 51 has an ion source 52 which includes a second filament 54 having a pigtail 54ptl and a second reflector 56, where these devices are formed in the same manner as filament 36 and reflector 38, respectively, discussed above in FIG. 2. The positioning of these devices differ, however, in that reflectors 38 and 56 are at opposing ends of arc chamber 51 while filaments 36 and 54 are in the same side of arc chamber 51 and they also are on the opposite side of arc chamber 34 as compared to the side in which arc slit 51s is formed. Lastly, note that filaments 36 and 54 are electrically connected in parallel to filament power supply 22.
The operation of architecture 50 is quite similar to that of architecture 30, with the example of a duplicate effect provided by using dual filaments and dual reflectors. Thus, once the power and potentials as described above relative to FIG. 2 are provided, each of filaments 36 and 54 emits electrons into interior area 51i, and those electrons are further directed toward the center of interior area 51i due to the electrical bias imposed on arc chamber 51 as well as the reflective action of reflectors 38 and 56 and the source magnets (not shown). Once more, these electrons may be combined with one or more gases in interior area 51i to create a final plasma from which ion beam 14 may be extracted.
Architecture 50 provides both improvements and drawbacks relative to various of the architectures described above. As an improvement, the use of dual filaments 36 and 54 improves the plasma density that may be achieved within interior area 51i of architecture 50. As a result, higher beam currents are associated with ion beam 14 of architecture 50. However, note that the drawbacks of architecture 50 are similar to those of architecture 30. For example, each of filaments 36 and 54 extends within interior area 51i and, thus, each filament is unprotected from the plasma and will wear as a result of such exposure. Indeed, this aspect may be more troublesome when there is reliance on dual components. In other words, the benefit of the dual filaments is lost if either one of filaments 36 or 54 fail and, thus, to the extent that both are needed then architecture 50 is limited in operation until the first failure of either filament, at which time the other filament may be effectively useless because ion source 52 will require down time to service at least the first-failed filament.
In view of the above, there arises a need to address the drawbacks of the prior art and to provide an improved integrated circuit ion source architecture, as is achieved by the preferred embodiments discussed below.
In the preferred embodiment, there is an ion implanting architecture. The architecture comprises an arc chamber having an interior area. The architecture also comprises a plurality of electron sources disposed at least partially within the interior area. Each of the plurality of electron sources comprises a conductive plate operable to emit electrons into the interior area and a heating element for transferring heat to the conductive plate. Other circuits, systems, and methods are also disclosed and claimed.